A traditional weight stack for use on what is known in the commercial fitness industry as “selectorized” or “Nautilus” strength training machines incorporates a weight stack in which similar or identically sized or shaped weight plates are stacked vertically atop one another. Formed into each plate and in identical locations on each plate in the are four throughbores: three throughbores extending vertically from the top surface through to the bottom surface of a given plate and one horizontally extending throughbore from the front surface (i.e., the surface facing the person selecting the weight level for the machine) through to the rear surface opposite the front surface. Two of the three vertical throughbores are of the same size and are located equally and on either side of the third, centrally located and larger vertical throughbore.
Inserted downward through the two smaller vertical throughbores are poles or “guide rods,” the purpose of which is to permanently affix the weight stack to the machine and to ensure proper alignment of the stack before, during and after the user performs an exercise on the machine. The third, centrally located and larger vertical throughbore is meant to accept a “selector stem” or third and moveable rod which is permanently attached to the topmost or highest plate on the weight stack but which is not permanently attached to any other plate in the stack. The selector rod is of at least equal length as the stacked plates forming the weight stack.
In these prior art systems, at the top of the selector stem a cable or belt which runs over a pulley or series of pulleys and/or cams and is attached at the other end to the “movement arm” which is the piece of the machine the user moves when performing the desired exercise. Formed horizontally through the selector stem are throughbores equal in number and vertically placed in an identical orientation to the horizontal throughbores formed from the front surface to the back surface of each individual weight plate. The purpose of this design is so that when a user wants to select the appropriate amount of resistance or weight desired to perform the exercise, that user inserts a “selector pin” into the horizontal throughbore on the surface of the weight stack and through the throughbore in the selector stem forming a non-permanent, selectable engagement so that when the user moves the movement arm, all plates above the temporary union formed by inserting the selector pin horizontally through the horizontal throughbore and selector stem are lifted vertically and against the force of gravity providing the strength training resistance when the user moves the movement arm and performs the exercise.
Although traditional weight stacks, such as those described above, have succeeded in carrying out the intended weight lifting purpose, there are many areas for substantial improvement.
One key problem often associated with traditional weight stacks is that the selector pin is removable and, as a result, is often misplaced, stolen or damaged whereupon it is replaced with a functionally and/or structurally inadequately sized pin. This inappropriate replacement historically has caused bodily injury when the system fails due to the violation of the inherent design of the apparatus.
The removable pin also permits the user to easily modify the operation of the apparatus outside the manufacturer's design criteria for the plates and/or weight stack, which can create unacceptable safety risks for the user and/or bystanders.
Additionally, there is a level of dexterity and hand to eye coordination required to insert the selector pin in the horizontal throughbore of the weight and the center post which further limits the true and effective result, and potentially frustrates the user such that the equipment receives less use.
In addition, an improper or incomplete mating between the selector pin and selector stem could result in an in situ decoupling with the weight stock dropping (through gravity) with potential for damage to the system and/or injury to bystanders standing in proximity to the weight stack.
Therefore, there exists a need for a safer, simpler and better arranged weight selection mechanism system such as the selector pin, car or ball and weight plate mechanism which cannot be misplaced, stolen or lost, and can be safely, simply and conveniently be engaged with thereby minimizing user error, complication and compromise in user safety.
Existing prior art approaches do not fully satisfy these problems. One approach calls for weight plates with rotating latches on the weight plates that once rotated engage with a groove molded into the center post (Itaru U.S. Pat. No. 5,306,221). This device, however, is overly complicated and unreliable with frequent slips and malfunctions.
There also exists a sliding plate mechanism (Reach U.S. Pat. No. 772,906), however, this approach also results in high manufacturing costs and creates inherent safety issues.
There also exists an imbedded system featuring a selector pin imbedded in a cartridge, imbedded in every weight plate and an external toggle lever switch mounted on the surface of each plate that is manipulated laterally from left to right on a weight stack (see, e.g., U.S. Pat. No. 7,608,021 to Nalley) by the user in order to engage the imbedded selector pin through the throughbore in order to engage the imbedded selector pin into the center post. This system is confusing to the user as one, more than one, or in fact all of the selector pins can be engaged at one time creating user confusion and numerous safety issues if and when the user mistakenly and dangerously attempts to perform an exercise with a weight amount he/she is physically incapable of lifting or moving.
Still another existing reference is to Pacheco (U.S. Pat. No. 8,152,702 B2) which purports to disclose a pulley based system which uppermost Weight plate of the plurality of Weight plates. A body is slidably coupled to the at least one rail. However this reference fails to teach the elimination of belts, pulleys or similar devices for transferring energy for the movement of a weight stack.
In addition to inherent safety issues in design or and confusion and unavoidable user error and/or injury, these latter devices and mechanisms are unable to be applied, added to or retrofitted onto existing exercise apparatus in the marketplace.